Note that not every antivirus alert is an actual infection. If your antivirus program catches a virus before it ever gets a chance to run on your computer, you’re safe. If it catches the malware later, you have a bigger problem.

Change Your Passwords

You’ve probably used your computer to log into your email, online banking websites, and other important accounts. Assuming you had malware on your computer, the malware could have logged your passwords and uploaded them to a malicious third party. With just your email account, the third party could reset your passwords on other websites and gain access to almost any of your online accounts.

To prevent this, you’ll want to change the passwords for your important accounts — email, online banking, and whatever other important accounts you’ve logged into from the infected computer. You should probably use another computer that you know is clean to change the passwords, just to be safe.

When changing your passwords, consider using a password manager to keep track of strong, unique passwords and two-factor authentication to prevent people from logging into your important accounts even if they know your password. This will help protect you in the future.

Ensure the Malware Is Actually Removed

Once malware gets access to your computer and starts running, it has the ability to do many more nasty things to your computer. For example, some malware may install rootkit software and attempt to hide itself from the system. Many types of Trojans also “open the floodgates” after they’re running, downloading many different types of malware from malicious web servers to the local system.

In other words, if your computer was infected, you’ll want to take extra precautions. You shouldn’t assume it’s clean just because your antivirus removed what it found. It’s probably a good idea to scan your computer with multiple antivirus products to ensure maximum detection. You may also want to run a bootable antivirus program, which runs outside of Windows. Such bootable antivirus programs will be able to detect rootkits that hide themselves from Windows and even the software running within Windows. avast! offers the ability to quickly create a bootable CD or USB drive for scanning, as do many other antivirus programs.

You may also want to reinstall Windows (or use the Refresh feature on Windows 8) to get your computer back to a clean state. This is more time-consuming, especially if you don’t have good backups and can’t get back up and running quickly, but this is the only way you can have 100% confidence that your Windows system isn’t infected. It’s all a matter of how paranoid you want to be.

Do you have Java installed? – Java is a huge source of security problems. The majority of computers on the Internet have an out-of-date, vulnerable version of Java installed, which would allow malicious websites to install malware on your computer. If you have Java installed, uninstall it. If you actually need Java for something (like Minecraft), at least disable the Java browser plugin. If you’re not sure whether you need Java, you probably don’t.

Are any browser plugins out-of-date? – Visit Mozilla’s Plugin Check website (yes, it also works in other browsers, not just Firefox) and see if you have any critically vulnerable plugins installed. If you do, ensure you update them — or uninstall them. You probably don’t need older plugins like QuickTime or RealPlayer installed on your computer, although Flash is still widely used.

Are your web browser and operating system set to automatically update? – You should be installing updates for Windows via Windows Update when they appear. Modern web browsers are set to automatically update, so they should be fine — unless you went out of your way to disable automatic updates. Using out-of-date web browsers and Windows versions is dangerous.

Are you being careful about what you run? – Watch out when downloading software to ensure you don’t accidentally click sketchy advertisements and download harmful software. Avoid pirated software that may be full of malware. Don’t run programs from email attachments. Be careful about what you run and where you get it from in general.

If you can’t figure out how the malware arrived because everything looks okay, there’s not much more you can do. Just try to follow proper security practices.

You may also want to keep an extra-close eye on your credit card statement for a while if you did any online-shopping recently. As so much malware is now related to organized crime, credit card numbers are a popular target.

even if i get a nagging adware, which i did a few weeks ago from a fan-speed download, i'll just go to my clean image and not deal with a clean up process. avast and kaspersky make good rescue disks to scan outside windows

Just because MSE has not been doing well in tests does not mean it makes you unprotected. In fact, MSE usually does pretty well in REAL WORLD tests - not antivirus tests where norton scores really well. Avast is really annoying and heavy on resources. If you want a light AV, choose Panda, not Avast.

Unfortunately that only works if a) you don't need Microsoft's other software products (so no good in most workplaces); b) you don't play most games; and c) you don't mind messing about for ages to get the distro working. Other than that, excellent advice

Unfortunately - in their infinite wisdom, MS does not require actual windows disks to be supplied with many inexpensive computers and laptops allowing them to save at least twenty cents by shipping the computer without this very important part of the package. Instead you are supposed to know enough about computers to make a recovery disk - which from my experience 99% of the users don't do. (did you?) Meaning that if the virus clobbered some important win file - such as the windows update - you are SOL.